1. Field of the Invention
The present invention relates to electronic timing circuits and, more particularly, to an electronic timing circuit that can be used to control a time period of fluid flow in residential and commercial showers, and the like.
2. Description of the Prior Art
The use of electronic circuits to control fluid flow in showers, faucets, commodes, and urinals is well known in the art. For example, U.S. Pat. Nos. 3,575,640, 4,823,414, 4,682,628, 4,984,314, and 4,651,777 all address various methods of employing electronic circuitry for controlling the flow of fluids in at least one of the previously stated types of washroom related fixtures. A brief description of these prior art devices is now given.
Ishikawa, U.S. Pat. No. 3,575,640, discloses an automatic water supply system that includes a capacity sensitive antenna for detecting the presence of a user. With the presence of a user detected, the antenna produces an active valve actuator signal that controls an electromagnetic valve to turn on a flow of water into a sink or urinal. A timer circuit and a delay circuit are included to shut off the water flow after a predetermined period of time has elapsed. A compensating circuit is included to determine the presence of an actual user, as opposed to an inanimate object or other unwanted capacity affecting phenomenon, and thus allows further water flow after a time-out has occurred and a user is still present.
Piersimoni, U.S. Pat. No. 4,823,414, teaches an automatically controlled faucet system wherein a light source and light sensor are used to sense the presence of a user, or object, under a faucet. Electronic circuitry is used to turn on and turn off a flow of fluid from the faucet in response to the presence and non-presence of a user, respectively, and also to terminate the flow of fluid from the faucet after a predetermined period of time has elapsed. Further fluid flow from the faucet is allowed after a time-out has occurred by simply having the user, or object, exit the sensing area under the faucet and then subsequently reenter.
Hill, U.S. Pat. No. 4,682,628, discloses a faucet system that includes an LED and a photo-detector which act together to detect the presence of a user, or object, in the vicinity of a faucet. When a user is detected, a solenoid drive circuit is triggered thereby permitting a flow of water from the faucet. A timer circuit is triggered along with the solenoid drive circuit so as to limit the time period of water flow. The timer circuit also prevents the solenoid drive circuit from permitting further water flow from the faucet until the user, or object, exits from the detection vicinity and then subsequently reenters.
Hardman, U.S. Pat. No. 4,651,777, discloses a water supply control system that includes a microphonic circuit which responds to audio signals. The microphonic circuit converts these audio signals into electrical signals that control a solenoid driven water valve assembly. Thus, water flow is controlled by sounds generated by or related to a user.
Lastly, in U.S. Pat. No. 4,984,314, Weigert, the inventor of the present invention, teaches an automatic fluid-flow control system that is configurable to be used in conjunction with faucets, commodes, urinals, and showers. In all cases, a light emitting device cooperates with a light sensor to detect light reflected from a user. A filtered and amplified output signal from the sensor is demodulated to provide a DC output signal that is used to control the flow of fluid in a manner appropriate to the particular configuration. As with several of the previously described prior art devices, a timer circuit prevents the flow of fluid after a predetermined period of time has elapsed, and further fluid flow is obtained by having the user exit and then subsequently reenter the light reflecting region.
Although all of the above-mentioned prior art devices perform certain desired functions in the context of controlling the flow of fluids, none address the situation where a specific time period of fluid flow is allotted for each user. Such a situation is desirable for reasons of fluid conservation and of overall fairness when a number of users are present. It is therefore desirable to overcome the shortcomings of the above-mentioned prior art devices in this area, while providing a simple, low cost, reliable, and highly accurate circuit that can be used to control the flow of fluid according to a specific time period that is allotted for each user.